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Topic: Full Frame Sharper Than Crop? (Read 32879 times)

libertyranger

So I've been doing some research and comparing different lenses on The Digital Picture's ISO comparison tool. What I am seeing is that the the same lens on both full frame and crop cameras shows a sharper image on the full frame camera. According to Ken Rockwell, he states that full frame will always be sharper. I know people don't like quoting him much, but from what I see, he appears to be right.

canon rumors FORUM

FF will deliver sharper results than crop in a situation like this one, where with the same lens the subject is shot from a greater distance with the APS-C camera. If the test was designed such that the camera-to-target distance was the same, and the target filled the APS-C frame but the FF image had to be cropped down by 1.6x, the APS-C image would be a little bit sharper.

But charts aside, I find that FF images are generally better than APS-C, for many reasons.

I suspect it may simply come down to the size of the photosites on a crop sensor. They tend to be smaller than those on full-frame sensor and thus the laws of physics and diffraction come in to play sooner on a crop sensor.

For a fuller and more in-depth answer just hang on, I see our friend Neuro on the horizon with his usual top-notch explanations for the witchcraft that is optical physics.

libertyranger

FF will deliver sharper results than crop in a situation like this one, where with the same lens the subject is shot from a greater distance with the APS-C camera. If the test was designed such that the camera-to-target distance was the same, and the target filled the APS-C frame but the FF image had to be cropped down by 1.6x, the APS-C image would be a little bit sharper.

But charts aside, I find that FF images are generally better than APS-C, for many reasons.

Thanks Neuro. I always look forward to your response on technical questions. I've been doing some portrait work as of late and given the same framing between the two formate, full frame would be the way to go for sharper images

i just went from a 7D to a 5D mk III. Both are incredibly sharp cameras when you have proper exposure and shutter speed. The difference i see is that the 5D mk III is much less noisy.. so it seems sharper in high ISO situations.

i will also say i know alot of people when they move from shooting JPG to RAW dont realize that they have to sharpen their images in post. With JPG's its done in camera, but with RAW you have to do the sharpening. it makes a difference.

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canon rumors FORUM

I think that the main difference is in in/correct focus, DoF and overal chip technology used and of course the mpx density in 100% magnification, which reveal all details of used glass.If I've changed, in the first link comparison of 50/1.4, the camera from 60d to 1dsII, center still looks much softer than real life photo...

Lenses will always perform 1.6x better in the center in FF. Corners might be worse. Since few people outresolve the sensor in everyday shooting at that 1.6x MTF boost is for all frequencies, I'd think FF would look much sharper for most.

bkorcel

My opinion is that any comparison between full frame and crop cameras is to use the same lens with the same subject and distance.

Further, my opinion using a 7D and 5D3 is that the 5D3 wins given all else being the same. The reason mainly is that you get some forgiveness with the increase in pixel density allowing you to crop if needed as well as the decrease in effective noise levels requiring less post processing artifacts.

Also one of the benefits (particularly with wildlife photography) is that the FF over the crop allows me to be more flexible when using primes as the recorded angle of view is slightly wider. Even if I have to crop the image slightly, I don't lose any IQ for the size I usually print to which is around 12 x 18"

I suspect it may simply come down to the size of the photosites on a crop sensor. They tend to be smaller than those on full-frame sensor and thus the laws of physics and diffraction come in to play sooner on a crop sensor.

For a fuller and more in-depth answer just hang on, I see our friend Neuro on the horizon with his usual top-notch explanations for the witchcraft that is optical physics.

Pah! Just as I type this, there he comes!

I have a question also. Diffraction. I have read about it, and there are several places that warns against closing the lens too much (some say you should not go to F22, but stay at F16 due to diffraction. Does anyone have a practical example on how this would alter a picture, besides a theoretical argument? Otherwise, when shooting landscape for instance, why would one not go minimum aperture all the time, given that you control the other factors?

canon rumors FORUM

You have to remember that lens resolution is not a single number. It's an MTF curve describing detail contrast for a given resolution. The higher the resolution, the lower the detail contrast. For a given number of megapixels, crop sensors use smaller pixels. That means detail is recorded at a lower point on the lens MTF curve...lower contrast...vs. a FF sensor.

So yes, FF DSLRs provide sharper images out of camera.

However, at low to mid ISO this is a non issue. All DSLR images (or at least all DSLR images with AA filters) benefit from sharpening, and most benefit from local contrast enhancement. You're going to sharpen the files either way. With crop you just sharpen more in your RAW converter or PS. If you want out of camera JPEGs, you turn up the camera sharpening a little more.

At high ISO this works against crop bodies because the sharpening enhances the noise. And it's at high ISO that I think FF really distinguishes itself. But for all the talk about FF vs. crop, at low to mid ISO there really isn't much difference. Nothing that would stand out even in a 24" print. (Even 4/3rds is capable of matching crop/FF with the same MP count at low ISO.)

Diffraction softens the image. At f/22 (FF) and f/16 (crop) the impact is enough that you cannot fully compensate with sharpening in post. I do not use f/22 on FF, and do not use f/16 on crop, except in very special circumstances. With landscape shots I try to use hyperfocal focusing and the largest aperture possible while still retaining the DoF I want. LiveView is great for evaluating this.

Note that diffraction does not impact any format more than any other for a given FoV and DoF.

I can only speak from my personal experience, but as far as I can see the answer is a resounding YES, IT IS.

I've got a 5DIII and a 60D. Indoors, the 5DIII totally crushes the 60D when it comes to sharpness & detail capture, even with the same lens. The 60D images tend to have a rough quality to them, even at reasonably low ISOs, and the 5D is just much cleaner. It becomes indistinguishable from 60D only from ISO 6400 up- but then again you wouldn't even USE the 60D at those ISOs...

Haven't tested outdoors in great lighting yet, but I'd think the difference might be less obvious there.